def main():
    numbers=[eval(x) for x in input().split()]
    N = numbers[0]
    M = numbers[1]
    list_numberOff = [eval(x) for x in input().split()]
    list_absent=[]
    present=0
    for i in range(1,N+1):
        if list_numberOff.count(i)==0:
            list_absent.append(i)
    if list_absent!=[]:
        print(" ".join(map(str,list_absent)))
    else:
        print(present)
main()